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I'm using wemos powered from li-ion 18650 with enabled Wi-Fi and photocell connected to A0 (10K voltage divider).Due to current spikes from ESP, voltage drops frequently about 500mV and photocell becomes unusable.I've tried electrolytic caps (470uF) as close to ESP as possible but it hasn't helped.

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- Mon Aug 14, 2017 8:48 am#69040
Why do you have 5v shown? Where's that coming from? An 18650 is 3.7v when fully charged (at best) so its not enough - by a long way - for anything requiring 5v and (technically) too high for the 3.3v pins.

My best suggestion is: Don't use a Li-Ion battery to power your project. try LiFePo if you have to use batteries.

Also, watch this: very informative - he compares 5 different sources for the ESP8266

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- Mon Aug 14, 2017 11:24 am#69048
I don't think it's the issue. 5V pin goes directly to RT9013 LDO which, according to the datasheet, has operation voltage from 2.2V to 5.5V. I thought that adding electrolytic capacitors will help, but unfortunately, it didn't.May I try tantalum or ceramic caps?